Continuous process for the recovery of paper broke containing a wet strength resin



April 12, 1966 ENMILLER ET AL 3,245,868 OCESS FOR THE RECOVERY OF PAPERBROKE CONTAINING A WET STRENGTH RESIN Flled Sept. 6, 1963 3 Sheets-Sheet1 CALENDER STACK Fl G zz 2O l4. s|zE PRESS If BREAKER STACK I IO 25 [81;, I6 PULPER scREw FEEDER 0 ACID 3 34 PULPERS 23 STEAM STOP VALVEDEWATERING 3| TUBE 27 35 COOKING TUBE VENT WATER cmp CHEST 35 CYCLONEDISCHARGER DII-UTIO/N CHEST SCREEN as j 42 I 37 I \V, ky 1.1L )AI r BLOWc'HEsT u|D cYcLoNE \WA HE 39 4o 43 5 Rs FIRST STAGE I sEcoND STAGE THIRDSTAGE SHREDDING DEWATERING COOKING WITH CHEMICALS g. I 1 3! 35' j scREwI FEEDER SHREDDER PRESSURE COOKING TUBE 27 CHIP CHES DEWATER SCR W ING ESTAGE FINAL CHEM FIFTH SIXTH STAGE I m sT'sskJE I l- [COMPLETE 1CLEANING, SCREENING, CYCLONE DEFIBERING THICKENING 0R WASHING I ANDRETURN TO SYSTEM. 35 35 FOURTH INVENTORS DISCHARGER HOWARD P.ESPENMILLER a BY ADAM I? BRIDGE STORAGE CHEST 2 w fi gg ATTORNEYS April12, 1966 p, EspENMlLLER ETAL 3,245,868

CONTINUOUS PROCESS FOR THE RECOVERY OF PAPER BROKE CONTAINING A WETSTRENGTH RESIN Filed Sept. 6, 1963 3 Sheets-Sheet 2 FIRST STAGE FIG 3SECOND STAGE I THIRD STAGE SHREDDING DEWATERING COOKING WITH CHEMICALS68 55 l is a? 5a SHREDDER 3 J HI DENSITY ATMOSPHERIC STORAGE COOKINGTUBE CHIP I CHEST J/J/ A J FouRTfi STAGE EIFTH STA-6E slxTi-l STAGEFINAL CHEMICAL TREATMENTasToRAeE COMPLETE cLEAN|Ne,scREEN|Ne,

, DEFIBERING. l THICKENING 0R WASHING 4 a RETURN To SYSTEM.

STORAGE CHEST FIRST STAGE 4 SECOND STAGE THIRD STAE SHREDDING DEWATERINGcooxme WITH CHEMICALS I I CHEMICAL HOT -I EMICAL 55 WATER HOT WATERDEWATERING I 60 scREw PULPER PULPER SHREDDER CHIP CHEST l FOURTH sTAEFINAL c'HEmcAL TREATMENT FIFTI-i STAGE SIXTH STAGE AND $TRAGE COMPLETECLEANING, SCREENING,

' DEFIBERING vTHICKENINGORWASHING L a RETURN TO SYSTEM.

y L INVENTORs 63 HOWARD P. ESPENMILLER a a BY ADAM R BRIDGE COOK CHESTSSTORAGE CHEST W awk 73 ATTORN EYS April 1966 1-1. P. ESPENMILLER ETAL3,245,868

CONTINUOUS PROCESS FOR THE RECOVERY OF PAPER BROKE CONTAINING A WETSTRENGTH RESIN Flled Sept. 6, 1963 3 Sheets-Sheet 5 FIRST STAGE ggcogoTAGE THIRD STAGE T; DEWATERING COOKING WITH CHEMICALS CHEMICAL v HOTwATER DEWATERING SHREDDER scREw PULPER JLE l I SCREEN CHIP CHESTN W Q lFOURTH STAGE F|NAL CREMICAL'TREATMENT AND STORAGE.

FIFTR sTAGEIsIXTH sTAeE COMPLETE CLEANING,SCREENING, DEFIBERING.THICKENING oR WASHING i 8RETuRN To SYSTEM. CHEMICAL CHEMICAL I HOT WATERi 1 HOT WATER I f 1 yr 1 DEWATERING COOK CHESTS STORAGE CHEST RiCOVEREDG*PHYSICAL TEST DATA AVERAGE +REFLECTMCE w T STREN TH FIBER FRM CAN.STD.TEAR MULLEN FREENESS FACTOR FACTOR FINES SHRINK PILOT PLANT 8 LABORATORY50-80 1.3-1.5 1.1-1.2 80-9012.9-14.2 803 -82.6%

B T s s 80 1.02 0.82 98 11 87.5%

CONTINUOUS 1 ggggf 80-98 154 1.13-1.22 78.5 12-13 82-83% COMPARED TO MgOINVENTORS AFTER 45mm. LAB. BEATING HOWARD P. ESPENMILLER 8 BY ADAM P.BRIDGE ATTORN EYS United States Patent 3,245,868 CONTINUOUS PROCESS FORTHE RECOVERY OF PAPER BROKE CONTAINING A WET STRENGTH RESIN Howard P.Espenmiller, Middletown, and Adam P.

Bridge, Franklin, Ohio, assignors to The Iflack Clawson Company,Hamilton, Ohio, a corporation of Ohio Filed Sept. 6, 1963, Ser. No.307,084 3 Claims. (Cl. 162-4) This invention relates to broke recoveryand more particularly to an improved apparatus and process for thecontinuous recovery of wet strength broke.

In recent years, more and more paper products have appeared whichcontain wet strength chemicals such as urea formaldehyde resins,melamine formaldehyde resins, and polya-mide resins, for example. Theseand other thermosetting resins are commonly employed to provide wetstrength and generally operate to bind the fibers of the paper to oneanother as a supplementary binding action over that usually present inan ordinary sheet which is held together by the interleaving,intertwining or matting of the paper fibers.

Heretofore, recovery of wet strength broke was done on a batch basisusing heat and chemicals and usually necessitating the removal of thebroke from the area of the machine to a storage area. The broke mayeither be sold to a processor who recovers the pulp or it may be treatedat the plant on a batch basis, and in some instances it is burnedbecause this may be the most inexpensive manner of disposing of it. Inany event, considerable manipulation and handling, as well asconsiderable storage area is required for the broke, all of whichpresents economical as well as practical problems.

Generally wet strength papers are made on high speed machines with dailytonnage rates in the order of 25 to 500 tons or more of wet strengthpaper or board per day. These relatively large machines usually operateon an automatic basis thus indicating the desirability of continuouslyor automatically processing the broke which accumulates during operationof the machine. This broke would include the trim and slabs from thefinished reels, culls or off-quality rolls which are cut up by a rollcutting machine, stored baled trimmings from the finishing operation, aswell as the broke which accumulates during abnormal operation of thepaper machine such as wet end trouble, breaks, and so forth.

Accordingly, it is a primary object of the present invention to provideimproved apparatus and process for the continuous recovery of wetstrength broke whereby substantially uniform operating conditions ofbroke recovery are maintained thereby providing substantially uniformquality stock for admixture with the stock at the wet end of the papermachine.

This and other objects have been achieved in accordance with the presentinvention by an apparatus which continuously receives the broke from themachine and shreds it or reduces it to a size and consistency so that itmay be transported to a dewatering assembly which increases theconsistency of the stock. Following the dewatering operation, the stockis continuously fed to a cooking station where it is treated withchemicals, prefererably :at elevated temperature and pressure to bringabout degradation or breakdown of the wet strength resin.

Following the chemical cooking operation, the stock is discharged andtreated to bring about final defibering, and then is washed andthickened and returned to the wet end of the machine, either as slurryor wet lap.

Another object of the present invention is the provision of an improvedapparatus for the continuous recovery of wet strength broke including ashredder or pulper to receive the broke from the machine and reduce itto an aqueous slurry, a continuous digester for treating the shreddedbroke to separate the wet strength resin from the fibers, and anappaartus for difibering the digested pulp mass to recover the useablefiber which is then fed to the broke chest for reuse on the machine.

A further object of the present invention is an improved method for thecontinuous recovery of wet strength broke whereby the broke is reducedto :a size small enough to allow transportation to a continuous digesterwhere it is treated to hydrolyze or bring about solution of thethermosetting resin, and continuously defibering the cooked pulp massfollowed by washing to remove the dissolved resins and cooking chemicalsto provide substantially uniform quality stock for admixture with thestock at the wet end of the machine.

Other objects and advantages of the invention will be apparent from thefollowing description, the accompanying drawings and the appendedclaims.

In the drawings:

FIG. 1 is a somewhat diagrammatic view of a continuous broke recoverysystem in accordance with the present invention;

. FIG. 2 is a diagramamtic view similar to FIG. 1 showmg the sequence ofsteps involved in a continuous broke recovery in accordance with thepresent invention;

FIGS. 3-5 are views showing modifications of the system illustrated inFIGS. 1 and 2; and

FIG. 6 is a chart showing comparative data of pulp recovered on a batchbasis and pulp recovered by the contmuous system of the presentinvention.

Referring to the drawings, which illustrate preferred embodiments of thepresent invention, FIG. 1 shows schematically a portion of the dryersection of a paper machine including dryer sections 10, 12 and 14 with abreaker stack 16 located between dryers 10 and 12, :and a size press 18located between dryer sections 12 and 14. The paper leaving the lastdryer 14 passes through a calender stack 20 and from there to a wind-upreel 22. Generally, it breaks are to occur on the dryer end of themachine, they occur either at the breaker stack 16, the size press 18,or the calender stack 20, resulting in the accumulation of a substantialamount of paper in a very short time.

The continuous recovery system in accordance with the present inventionis preferably associated with the dry end of the machine and includespulpers 23, 24 and 25 located below the level of the paper machine torece1ve the broke from the breaker stack, size press, and calenderstack, respectively. Satisfactory results have been achieved using forpulper 25, a pulper available from The Black Clawson Company under thetrademark hydrapulper and described more fully in US. Patent 3,073,535issued January 15, 1953, and assigned to the same assignee. Also, apulper available from The Black Clawson Company under the trademarkSydrapulper" has proven satisfactory for use as pulpers 23 and 24.

As the broke enters the pulpers, it is mixed with water and shredded toa chip size of about inch square to rectangular pieces about /2 inchwide and 1 inch long, and having a consistency of the pulp such that itcan be continuously fed to a chip chest 27 which acts as a storagestation. From the chip chest 27, the pulp mass is introduced into aninclined screw operated dewatering tube 30 wherein pulp consistency isincreased and from the dewatering tube, the pulp passes through a screwfeeder 31 which again increases the pulp consistency While alsopreferably reducing the chip size to about one third its original size.The dewatering tube and the screw feeder are conventional items, as iswell known in the art.

The discharge end of the screw feeder is connected to the horizontallyarranged continuous digester tube 33 which includes a variable speedscrew flight and which forms a cooking station in which the chip mass istreated to break down the fiber-to-fiber bond and thus permit separationof the fibers. Satisfactory results have been achieved in accordancewith the present invention with the use of a cooking or digesting tubeavailable from The Black Clawson Company under the name ContinuousPandia Digester, and described more fully in the Beveridge et al. Patent2,323,194 issued June 29, 1943.

The chip mass continuously extracted from the screw feeder 31 is treatedin the cooking station by a minimum mechanical treatment, and issimultaneously chemically treated to react with the resin on the fiber,as by hydrolysis with chemicals, both treatments being conducted withoutsignificant degradation of fiber quality. The continuous digester of thetype previously described operates satisfactorily to bring about bothtypes of treatment simultaneously. The cooking station also includesmeans to supply steam, chemicals and Water for treating the paper chipmass during the digesting operation. Also chemicals can be added aftercooking to neutralize the pulp mass if this is desired or necessary.

The nature and/ or degree of chemical treatment varies somewhatdepending on the nature and content of the wet strength resin, and wetstrength of the particular type paper itself which is directly relatedto the dry strength of the sheet. Certain operations in the preparationof the stock such as Jordaning and refining assists in developing orincreasing dry strength of the sheet, and the increased dry strengthtends to increase the wet strength of the sheet for any given resincontent. For example, a kraft bag sheet has more dry strength than atissue sheet, and accordingly, the kraft bag sheet has a greater wetstrength based on an equivalent usage of a given wet strength resin.Moreover, the retention of the wet strength resin by the fiber of thepulp is proportional to the purity of the fiber, i.e., the permaganatenumber; and ground wood, which has a relatively high permanganate numberhas a low retention of wet strength resin when compared to rag pulpswhich have a low permagnate number.

Based on these considerations, as well as the nature and percentage ofwet strength resin, the conditions and time of cooking within thecooking station are coordinatedand correlated so as to bring aboutpartial separation of the fiber by mechanical action with a simultaneouschemical action in which the wet strength resin is brought to an aqueoussoluble condition, for example, by the use of an acidic material.Preferably the chemical action is one of hydrolysis in which thefunctional groups of the resin are hydrolyzed at a predetermined pH tobring about a conversion of the wet strength resin to a soluble polymer,and thus the resin bond is removed from the pulp fiber thereby allowinga substantially complete separation of the fibers constituting the pulpmass.

From the cooking tube or vessel 33, the digested or cooked pulp mass isdischarged through discharger apparatus 35 and treated with water whilepassing through a pressure reducing cyclone 36 lowering the pump mass inconsistency and temperature and venting steam to the atmosphere, thusbringing the cooked pulp mass to atmospheric pressure and dischargingthe pulp mass from the apex of cyclone 36 into blow chest 37. The pulpmass is then pumped with consistency regulation, preferably 4% to 6%through rotary refiner 39 which substantially produces completedefibering of the pulp mass. The defibered pulp mass discharges into adilution chest 40 where the consistency is lowered, preferably to 0.5%to 1.0% consistency. From the dilution chest 40, the stock is forced bypump to a cyclone 42 wherein high specific gravity foreign materials areremoved. Since the stock leaving the cyclone 42 may contain lumps orbundles of fibers, it is preferably treated with a rotary screen 43which brings about particle size separation in a single pass of the pulptherethrough with a minimum possibility that any lumps or bundles canslip through without being rejected. Satisfactory results have beenachieved utilizing a rotary screen available from The Black ClawsonCompany under the trademark Selectifier Screen, described more fully inthe Martindale Re. 24,677 patent issued July 28, 1959, and assigned tothe same assignee.

From the screen the stock is washed by vat type washers 44 to removecooking chemicals and dissolved resin if this is desired or necessary inorder to reuse the recovered fiber. It is then returned to the brokechest where it is blended with the normal stock furnish being fed to thewet end of the paper machine according to standard paper makingpractices.

The dewatering tube 30, the screw feeder 31, and the cooking tube 33 arepreferably equipped with variable speed drives so that the retentiontime therein may be varied to provide a maximum output during the breakperiod, while standard consistency regulators and flow control valvesfor stock and water are provided so that the system may be operatedautomatically, if desired. These assemblies are individually well knownin the art.

The sequence of operations carried out on the broke may be understoodwith reference to FIG. 2, wherein like reference numerals have been usedwherever possible. In the first stage in which the broke is shredded bya shredder or pulper 25, the broke may be treated with water, and ifnecessary some chemicals may be added to assist in the mechanicalreduction in the size of the broke to such a particle size that it canbe transported or pumped to the various other stations for subsequenttreatment. With a pulper 25 of the type previously described, the stockmay have a consistency of between about 1% and about 10% with apreferred consistency being in the range of about 4%. From the pulper 25the stock enters the chip chest 27 which is preferably large enough totake about 30% of the daily capacity of the recovery system. Assumingthe system is capable of handling 30 tons of broke per day, chip chest27 would have a capacity of about 18,000 pounds or approximately betweenabout 2% to 5% of the maximum output of the paper machine. Here, themass of paper chips may be stored, and the consistency thereof adjusted,if necessary, to provide a uniform consistency of between about 3 /2% to4 /2%.

After shredding, the stock is dewatered by treatment with the dewateringtube 30 which increases consistency to about 10% and the screw feeder 31so that the stock consistency is increased to between 35% and about 65%,and preferably in the range of 50%. By means of a dewatering tube 30,the stock may be dewatered by free drainage to a consistency of about10%, and the consistency increased by the screw feeder 31 to betweenabout 35% to about 65%. This increase in consistency is desirable in theevent that pressure and elevated temperatures are to be used during thecooking cycle since it operates to prevent blow back or back flow of thechip mass from the cooking station in the event that cooking isconducted under pressure.

Following the dewatering operation the stock consistency is furtherincreased to between 35% and 65% and preferably in the range of about50% and treated at a predetermined pH to bring about partial separationof the fibers by mechanical working, as well as separation of the resinfrom the fibers by chemical cooking, In the fourth stage of treatment,the stock discharged from the cooking station is passed through cyclone36 to a storage chest 40 where the consistency is adjusted for thesubsequent defibering operation which forms the fifth stage. In thesixth stage, stock is washed clean of cooking chemicals and dissolvedresin, thickened and returned to the system which feeds the wet end ofthe machine.

In operation, assuming there is no break on the paper machine, the trimand slabs from the finished reels may be shredded by pulper 25 whichcontinuously feeds chip chest 27. Off quality rolls or culls which havebeen cut in half by a roll splitting mechanism may be shredded by eitherone of pulpers 23- and 24 and similarly fed to the chip chest 27. Inthis no break condition stored baled trimmings may also be reprocessed.The stock from the pulpers 23, 24 and 25 flows through a consistencyregulator (not shown) to the chip chest 27 and into the other apparatusforming the continuous recovery system, and during this time the rate ofproduction is relatively low.

In the event of a break, the entire output of the machine must now behandled by the recovery system, and as the paper enters the pulpersrapidly, the amount of water fed to the pulpers is increased. As theshredded stock is extracted, the consistency regulator between thepulpers and the chips chest maintains the proper stock density to thechip chest, wherein the level begins to rise. The sudden increase in thelevel in the chip chest indicates that the full production of the papermachine is being handled by the recovery system, and provides anindication by an alarm system so the operator may know that there is infact a break on the machine. By suitable adjustments, the rates of flowof liquid, consistency of the stock, and retention time within thevarious tubes may be controlled. For example, the number of revolutionsper minute of the screw feeder is increased, the valve on the dischargeropens up slightly to take care of the extra capacity while stillmaintaining the proper cooking conditions within the digester 33, andthe entire sequence of operations is increased to maintain constant anduniform treatment of the fiber during the maximum production period.

Once the break is over, this will be indicated by a reduction in thelevel of stock within the chip chest, and the entire system may beslowed down to the capacity it had during the no break condition of thepaper machine.

One of the features of the present invention is the provision of acontinuous system for treating the paper chip mass to eifect mechanicalseparation of the fibers along with chemical separation of the wetstrength chemical which tends to bind the fibers to one another. Thechemical treatment is provided by the horizontally arranged digestertube previously referred to and generally includes a hydrolysis of thewet strength resin at an elevated temperature and pressure. For example,in the case of urea formaldehyde resins the pulping may be accomplishedat a pH from about 3.0 to 4.5 and at a temperature in the range of 150F. to 212 F., and with this particular type resin it is preferred thatthe pulp con sistency be relatively high for example above about In thecase of papers using a melamine or urea formaldehyde resin, the resinmay be hydrolyzed at a pH of between about 2.0 to 4.5, obtained withsulphuric acid, at a pressure of about psi. and a temperature of about300 F. for a period of time sufficient to bring about chemicaldegradation of the resin. This may require from about 5 to 20 minutesdepending on the nature of the base stock and the percentage of resinutilized.

One of the more diflicult wet strength resins to handle are thepolyamide series, and best results are obtained at a pulping consistencyof about 8% at a pH of about 11.5 and at a temperature of about 120 F.using caustic soda in an amount equal to about 4% based on the oven dryweight of the fiber. Pulping of this type resin may also be accomplishedin the pH range of 10 to 11.5 and at temperatures ranging from 100 F. to200 F.

Since the chemical action is primarily one of hydrolysis, any acid oracid generating material may be utilized, and as a general rule fivepounds of concentrated acid per ton of air dried fiber providesatisfactory results. The amount of chemical used for hydrolysis isdependent upon the percentage of wet strength chemical present in thewet strength broke and the type and grade of broke being processed.

It is possible in accordance with the present invention to utilize asomewhat different form of apparatus and diiferent cooking conditions tobring about separation of the wet strength resin and provide a mass offibers which have not been degraded to the point where they are nolonger useful. Referring specifically to FIG. 3, the first stage isbasically the same as the first stage previously described. However, thesecond stage or dewatering stage is now accomplished by a dewateringscrew with a high density storage chest 56 and a horizontally arrangeddigester tube 58 receiving the pulp mass for the simultaneous mechanicaland chemical separation of the fiber. In this particular modification,cooking is carried out under atmospheric conditions but at an elevatedtemperature (212 F.) Approximately 60% of the dwell time of the cookingstage would be in the high consistency storage chest 56 with theremaining 40% needed to hydrolyze the wet strength resin being in thecooking tube. The remaining portion of the system is similar to thatdescribed previously.

In another modification shown in FIG. 4, which is somewhat similar tothat shown in FIG. 3, cooking is carried out in two pulpers 60 and 62which are arranged in series, pulper 60 reducing the shredded mass ofpaper chips to a somewhat smaller size than provided by shredder orpulper 25, and pulper 62 operating to reduce the size of the chip evenfurther. Pulper 62 then discharges alternately into cook chests 63 and64, with both of the chests emptying into a common storage chest 65.Approximately 30% of the dwell time would be in pulper 60, 30% in pulper62 and 40% in the cook chests. The subsequent stages of defibering andcleaning, screening, thickening or washing are the same as thosepreviously described.

Referring now to FIG. 5, the chip mass from the dewatering screw 55 isreceived by a pulper 68 wherein the chip mass is treated with chemicalsand hot water, and the extracted pulp is fed to a rotary mechanicalscreening assembly 70 whose operation is similar to that of the rotaryscreening assembly 43 described in connection with FIG. 1. The rejectsfrom screen 70 may be fed back into the pulper 63 for furtherprocessing. From the screen 70 the extracted pulp is dewatered bydewatering screw 72 to thicken the stock by free drainage, and the pulpis alternately fed to cooking chests 73 and 74 to complete chemicalseparation of the wet strength stock and resin. In this system,approximately 30% of the dwell time would be in the pulper 68, 10% inthe screen 70 and about 60% in the cooking chests 73 and 74, the pulpfrom the cook chests being pumped to storage chest 65. The fifth andsixth stages may be of the type previously described.

One of the important advantages of the continuous recovery system of thepresent invention may be under stood with reference to FIG. 6 whichshows a comparison of pulp recovered on a continuous basis from a pilotplant and laboratory system pulp recovered on a batch basis, and pulprecovered on a continuous basis in a large scale installation. Inaddition .to the elimination of storage and handling of the broke, whichin itself is a substantial advantage, the system in accordance with thepresent invention unexpectedly produces pulp which is far better thanthe pulp produced on a batch basis. Significant is the fact that thepulp from the continuous large scale installation was better in qualitythan either the batch or pilot plant system.

These unexpected and superior results of the continuous system may, inpart, be attributable to the fact that the volume of material beinghandled at any one point in the system is substantially less than thathandled on a batch basis, and thus more precise control of variousconditions is possible. While the amount of pulp or raw material beinghandled at any one time by the continuous system may be less than theamount handled on a batch system, the total output of the continuoussystem is equal to, and may exceed the total output of a batch recoverysystem. Not only is the pulp from the continuous system of improvedquality, but there is also the advantage of eliminating the storage andhandling as previously described.

While the methods and forms of apparatus herein described constitutepreferred embodiment of the invention, it is to be understood that theinvention is not limited to these precise methods and forms ofapparatus, and that changes may be made therein without departing fromthe scope of the invention which is defined in the appended claims.

What is claimed is:

1. A method for the continuous recovery of paper broke from a papermachine wherein the paper has been treated with a wet strengththermosetting resin for imparting said strength characteristics thereto,comprising the steps of continuously shredding the broke receiveddirectly from said machine in the presence of water to provide a chipmass dispersed in water of consistency between 1% and 10%, continuouslydewatering said chip mass to increase the consistency thereof to between10% and 65%, adding chemical to hydrolyze the thermosetting resin forsolubilizing a substantial portion thereof, said chemical being added inan amount to provide a pH of between 2.0 and 12.0, continuously cookingsaid chip mass at a consistency of between 4% and 65% at a temperaturebetween 100 F. to 300 F. for a period of time suflicient to hydrolyzethe thermosetting resin thereby forming a pulp mass wherein the resin issubstantially completely separated from the pulp fibers, and thereaftercontinuously washing said pulp mass to remove the dissolved resins andthe chemicals to provide a pulp mass free of thermosetting resin andchemical.

2. A method as set forth in claim 1 wherein said cooking chemical isadded in an amount sufiicient to provide a pH of between about 10.0 and11.5 for hydrolysis of said thermosetting resin.

3. A method as set forth in claim 1 wherein said cooking chemical isadded in an amount sufficient to provide a pH of between 3.0 and 4.5 forhydrolysis of said thermosetting resin.

References Cited by the Examiner UNITED STATES PATENTS 2,394,273 2/ 1946Thomas 1624 2,697,661 12/ 1954 Hollis 1624 2,872,313 2/1959 House et a1.162-6 2,910,398 10/ 1959 Durant et a1 1624 2,977,274 3/1961 Hollis 16243,057,769 10/ 1962 Sandberg 1624 DONALL H. SYLVESTER, Primary Examiner.HOWARD R. CAINE, Examiner. S. L. BASHORE, Assistant Examiner.

1. A METHOD FOR THE CONTINUOUS RECOVERY OF PAPER BROKE FROM A PAPERMACHINE WHEREIN THE PAPER HAS BEEN TREATED WITH A WET STRENGTHTHERMOSETTING RESIN FOR IMPARTING SAID STRENGTH CHARACTERISTICS THERETO,COMPRISING THE STEPS OF CONTINUOUSLY SHREDDING THE BROKE RECEIVEDDIRECTLY FROM SAID MACHINE IN THE PRESENCE OF WATER TO PROVIDE A CHIPMASS DISPERSED IN WATER OF CONSISTENCY BETWEEN 1% AND 10%, CONTINUOUSLYDEWATERING SAID CHIP MASS TO INCREASE THE CONSISTENCY THEREOF TO BETWEEN10% AND 65%, ADDING CHEMICAL TO HYDROLYZE THE THERMOSETTING RESIN FORSOLUBILIZING A SUBSTANTIAL PORTION THEREOF, SAID CHEMICAL BEING ADDED INAN AMOUNT TO PROVIDE A PH OF BETWEEN 2.0 AND 12.0, CONTINUOUSLY COOKINGSAID CHIP MASS AT A CONSISTENCY OF BETWEEN 4% AND 65% AT A TEMPERATUREBETWEEN 100%F. TO 300*F. FOR A PERIOD OF TIME SUFFICIENT TO HYDROLYZETHE THERMOSETTING RESIN THEREBY FORMING A PULP MASS WHEREIN THE RESIN ISSUBSTANTIALLY COMPLETELY SEPARATED FROM THE PULP FIBERS, AND THEREAFTERCONTINUOUSLY WASING SAID PULP MASS TO REMOVE THE DISSOLVED RESINS ANDTHE CHEMICALS TO PROVIDE A PULP MASS FREE OF THERMOSETTING RESIN ANDCHEMICAL.